The present invention relates generally to the building and construction trades and is more particularly directed to devices for marking pairs of aligned positions for installation of various assemblies.
A certain type of burglar alarm system employs a small magnet, which is installed in an edge of a door or window, and a magnetically sensitive switch, which is installed in the door frame or window frame at a position opposite the magnet. For reliable operation of the alarm system the magnet has to be aligned precisely opposite the switch when the door or window is closed. In the past to install such a magnet/switch pair, an installer generally first installed one unit of the pair (either the magnet or the switch) by drilling a hole at the desired location to receive the unit. The installer then proceeded to make a series of measurements from the first hole to determine the location of the second hole in the opposing window, door or framing member for the other unit of the pair. This procedure takes time and can lead to inaccuracies if not carefully carried out because a slight error in one measurement can be compounded as the several measurements are made to locate the second unit.
The same problem arises in other contexts, too. For example, when installing a door knob a hole is drilled in the edge of the door through which the latch bolt protrudes and a cutout is typically made for a covering faceplate. A matching hole is drilled in the doorframe at a position to receive the latch bolt and a similar cutout is formed for an opposing striker plate. Here, too, it is necessary that the cuts be positioned precisely for the door to latch properly.